1. Field of the Invention
This invention relates to a projection type large-size screen display apparatus.
2. Description of the Related Art
Hitherto, there has been developed a large-size screen display apparatus for displaying a single image on a screen having a size of 40 inches or thereabouts by merging optical images formed on respective monochromatic cathode-ray-tubes in red, blue, and green with the size of 7 inches. This conventional large-size screen display apparatus has several disadvantages such as a drop in brightness due to the increase in the projection magnification factor necessary for effecting display on a large-size screen, and the increase in volume of a cabinet for securing a long projection distance.
As a large-size screen display apparatus which is capable of effecting display on a large-size screen while the size of the apparatus and the brightness of the picture are maintained, there is known a large-size screen display comprising a plurality of projection display devices having the size of 40 inches or thereabouts arranged in a matrix layout.
FIG. 7 of the accompanying drawings is a schematic representation of a conventional multi-display apparatus having a plurality of projection display apparatuses arranged in a matrix. In FIG. 7, the reference numeral 500 designates a rear-projection type projection display device. This projection display device has a display screen consisting of a column line including four of the projection display devices 500 and a row line including four of the projection display devices 500, and each projection display device 500 displays an enlarged subdivision of one picture frame by the use of a video signal quadrupled both longitudinally and laterally.
FIG. 8 is a cross sectional view of the projection display device 500 of FIG. 7. In FIG. 8, the reference numeral 501 designates a cathode-ray-tube (hereinafter referred to as CRT); 502, a projection lens; 503, a projection screen; 504, a screen frame; 505, a housing for accommodating and supporting the CRT 501 and the projection lens 502.
An enlarged subdivisional image formed on the CRT 501 is projected onto the projection screen 503 through the projection lens 502. The projection screen 503 is attached to the housing 505 with the periphery thereof fixed in a groove of the housing. One large-size screen is made up of a plurality of projection screens 503 arranged planarly in a matrix layout, each being mounted to the corresponding screen frame 504. This thereby produces the large-size screen display apparatus shown in FIG. 7.
The conventional large-size screen display apparatus having the above structure causes non-display areas having a stripe shape to appear longitudinally and laterally on the projection screen due to the presence of the screen frame for securing the projection screen in the optical path when the plural projection display apparatuses are arrayed in combination, which impairs the picture quality.